This invention relates to a synthetic peptide, an assay kit and an assay method of human Mn (manganese)-superoxide dismutase (hereinafter abbreviated as Mn-SOD) by use thereof.
Human Mn-SOD is an enzyme (with a molecular weight of one domain being about 25,000, and considered to comprise dimer or tetramer thereof) existing in the matrix portion of mitochondria, and catalyzes the reaction which disproportionate the superoxide anion radical (O2.sup.-) which is the primary molecular species of active oxygen as shown below: EQU 2 O.sub.2.sup.- +2 H.sup.+ .fwdarw.H.sub.2 O.sub.2 +O.sub.2
Whereas, measurement of human Mn-SOD concentration of serum in liver diseases has been considered to be of high diagnostic significance according to the investigations by use of polyclonal antibodies (Pharmaceutical Journal: Inagaki, Sawaki, 20, 1, 1984; The 5th Tumor Marker Research Meeting: Iizuka, Arai et al, 1985). Also, Taniguchi et al have shown that human Mn-SOD concentration is higher in lung cancer according to the immunological method by use of a polyclonal antibody prepared by immunization of a goat (Journal of National Cancer Institute, 72, 5, 1984). Thus, importance of human Mn-SOD concentration in serum has been pointed out.
Accordingly, for assaying human Mh-SOD concentration in serum, it has been required that human Mn-SOD can be assayed inexpensively, simply and at high sensitivity by use of an enzyme-labelled monoclonal antibody having high specific reactivity against human Mn-SOD, a peptide capable of reacting competitively with human Mn-SOD against the monoclonal antibody, and human serum, in place of the use of the polyclonal antibody against human Mn-SOD of the prior art. However, no such assay method has been known.